我有一个多态表creationables
,但无法找出基于creationable_type
返回所有creationables
的条件查询的关键部分> 字段值(人类
或 机器人
),基于它们是否从各自的表中删除(人类
、机器人
,以及 robots
和 robot_upgrades
组合)。以下是伪查询后的 4 个表:
<强>1。可创作
| id | creationable_type | creationable_id | robot_upgrade_id | is_activated
----------------------------------------------------------------------------
| 1 | human | 1 | 0 | 1
| 2 | robot | 1 | 0 | 1
| 3 | robot | 2 | 1 | 1
<强>2。人类
| id | name | deleted
---------------------
| 1 | Adam | NULL
<强>3。机器人
| id | name | deleted
------------------------
| 1 | Droid X | NULL
| 2 | Droid Y | NULL
<强>4。机器人升级
| id | upgrade_name | deleted
--------------------------------
| 1 | Patch V4 | NOW()
伪查询:
SELECT *
FROM creationables
// If creationable_type == 'human'
// we want to get non deleted humans
JOIN humans ON humans.id=creationable_id WHERE humans.deleted=NULL
// If creationable_type == 'robot' and robot_upgrade_id == '0'
// we want to get non deleted robots
JOIN robots ON robots.id=creationable_id WHERE robots.deleted=NULL
// If creationable_type == 'robot' and robot_upgrade_id != '0'
// we want to check both robots and robot_upgrades tables
// and if either of them was deleted we do not want to return them
// we want to get non deleted robots/robot_upgrades combo
JOIN robots ON robots.id=creationable_id WHERE robots.deleted=NULL
JOIN robot_upgrades ON robot_upgrades.id=robot_upgrade_id WHERE robot_upgrades.deleted=NULL
WHERE creationables.is_activated = '1'
知道基于伪查询中的注释正确的条件查询是什么吗?
更新 这是fiddle
预期结果应如下所示:
| id | creationable_type | creationable_id | robot_upgrade_id | is_activated
----------------------------------------------------------------------------
| 1 | human | 1 | 0 | 1
| 2 | robot | 1 | 0 | 1
不应返回 id 为 3 的 creationables
行,因为即使其机器人未从 robots
中删除,其相关的 robot_upgrade_id
1 也会被删除在robot_upgrades
中。
最佳答案
没有直接的方法可以做到这一点。 INNER JOINS 将排除第一个 JOIN 之后的前面的类型,因此您可以使用 LEFT JOINS 执行如下操作:
SELECT *
FROM creationables A
LEFT JOIN humans ON humans.id= A.creationable_id AND A.creationable_type = 'human' AND humans.deleted is NULL
LEFT JOIN robots ON robots.id= A.creationable_id AND A.creationable_type = 'robot' AND robots.deleted is NULL
LEFT JOIN robot_upgrades ON robot_upgrades.id=A.robot_upgrade_id AND A.creationable_type = 'robot' and robot_upgrade_id != '0' AND robot_upgrades.deleted is NULL
WHERE creationables.is_activated = '1';
或者您可以尝试像这样的 UNION 方法:
SELECT * FROM creationables A JOIN humans ON humans.id= A.creationable_id AND A.creationable_type = 'human' AND humans.deleted is NULL
UNION
SELECT * FROM creationables A JOIN robots ON robots.id= A.creationable_id AND A.creationable_type = 'robot' AND robots.deleted is NULL
UNION
SELECT * FROM creationables A JOIN robot_upgrades ON robot_upgrades.id=A.robot_upgrade_id AND A.creationable_type = 'robot' and robot_upgrade_id != '0' AND robot_upgrades.deleted is NULL
WHERE creationables.is_activated = '1';
如果机器人更新被删除,它也不应该返回机器人,那么您可以使用此查询代替:
SELECT A.creationable_type, humans.name, null as "update"
FROM creationables A
JOIN humans ON humans.id= A.creationable_id AND A.creationable_type = 'human' AND humans.deleted is NULL
UNION
SELECT A.creationable_type, robots.name, robot_upgrades.upgrade_name as "update"
FROM creationables A
JOIN robots ON robots.id= A.creationable_id AND A.creationable_type = 'robot' AND robots.deleted is NULL
LEFT JOIN robot_upgrades ON robot_upgrades.id=A.robot_upgrade_id AND A.creationable_type = 'robot' and robot_upgrade_id != '0' AND robot_upgrades.deleted is NULL
WHERE A.is_activated = '1' AND robots.id NOT IN
(SELECT DISTINCT A.creationable_id FROM creationables A
JOIN robot_upgrades ON robot_upgrades.id=A.robot_upgrade_id AND A.creationable_type = 'robot' and robot_upgrade_id != '0' AND robot_upgrades.deleted is NOT NULL);
这些可能不是最好的方法,但可以完成工作,希望这有帮助!
关于MySQL - 基于多态表值的条件查询结果?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/56230943/